This proposal is aimed toward elucidating the genomic arrangement and nucleotide sequence of sex-related repetitive DNA molecules in the genome of the domestic chicken and bobwhite quail. These studies are initiated by examining the highly repetitive DNA sequences, often called satellite DNA, in the white leghorn chicken. Because of a greater amount of repetitive DNA in the female chicken than in the male, experiments were initiated to look for specific DNA sequences associated with the sex chromosomes. Over the last two years primary efforts have been directed toward elucidating the role of the sex linked DNA sequence in rds. Two kinds of sex-related DNA sequences (0.4kb and 1.1kb) from two species of birds, Colinus virginianus and Gallus domesticutus have been isolated, purified and characterized. Competitive DNA-DNA hybridization, gel electrophoresis and restriction enzyme analyses support the limitation of these DNA sequences to the heterogametic sex (female). A detailed characterization of the structure and genomic organization of these sequences is the focus of the current work. Cloning and sequencing eh 0.4kb and 1.0kb Xhol fragments isolated from gels will be the first priority. These clones will then be used to screen genomic blots and genomic libraries to derive a detailed picture of the overall organization of the female-specific sequences. Both the cloned and gel purified fragments can be used for the in situ studies; however, the homology between chick and quail sequences can be determined by direct sequence comparison.